The present invention relates generally to a method and system for reducing the level of contaminants in a body of groundwater and more particularly to a bioremediation method and system for groundwater treatment.
Groundwater contamination, typically arising from petroleum storage tank spills or from intentional or accidental discharge of liquid hydrocarbons or compositions containing same, has become a problem of increasing concern. This type of contamination occurs not only at industrial complexes, but also in suburban neighborhoods, which would appear to be havens from such phenomena. The source of contamination in suburban neighborhoods or areas is very commonly automobile service station sites at which antiquated or abandoned storage tanks have released gasoline, fuel oils, lubricants, and the like into the local groundwater. Other common sources of such noxious materials can include dry cleaning establishments and/or manufacturers or distributors of the tetrachloroethane which is used in the dry cleaning process.
Various remediation techniques have been utilized in the past for the treatment of contaminated groundwater in order to reduce or eliminate the contaminants. One of the most widely used systems is one based on so-called xe2x80x9cpump and treatxe2x80x9d technology. These systems withdraw the contaminated groundwater and a phase-separated product from a recovery well located in the groundwater and pump it to an above ground treatment facility. Thereafter, various treatment techniques, as are well known, are used to remove contaminants from the displaced groundwater. These xe2x80x9cpump and treatxe2x80x9d systems are relatively expensive to install and require that the remaining contaminants, which have been separated from the groundwater, be disposed in an environmentally friendly manner. These processes further increase the cost of the techniques.
One example of a known remediation system is disclosed in U.S. Pat. No. 5,286,141. The ""141 patent teaches oxidizing the source of groundwater contamination to harmless constituents by locating a plurality of mutually spaced wells into a groundwater region. A treating flow of hydrogen peroxide solution is provided into the groundwater from one or more wells. The treating flow typically contains reaction surface enhancing reagents, which provide increased surfaces at which the reaction between the hydrogen peroxide and the hydrocarbon contaminants may occur. Further, a catalytic agent is also preferably incorporated into the treating solution or as a pre-injection into the groundwater region to promote the desired reaction between the hydrogen peroxide and hydrocarbons.
Recently, there has also been increasing interest in bioremediation technology. However, its use in treating groundwater has been relatively ineffective due to the complexity of the procedures and equipment required, including expensive and complex reactors. Moreover, current bioremediation techniques can cause adverse geochemical reactions and can introduce new toxic compounds into the groundwater. Additionally, current bioremediation systems, still require the use of non-organic catalysts or additives to cause the process to be completed in a reasonable period of time. These catalysts or additives raise other contaminant issues with respect to the groundwater.
It is known that naturally growing bacteria in the groundwater can break down groundwater contaminants. However, these bacteria feed off oxygen and the lack of oxygen is the single biggest limiting factor on the growth of the bacterial population and therefore contaminant decrease. Ambient air, which is comprised of about 21% percent oxygen, only results in approximately 10-12 ppm of dissolved oxygen in the groundwater and thus is not sufficient to adequately destroy or reduce contaminants. Various attempts to increase the amount of oxygen by utilizing oxygen releasing compounds have been tried, but these oxygen releasing compounds, such as magnesium peroxide or calcium peroxide are expensive. Further, these oxygen releasing compounds only produce a small amount of usable oxygen and therefore do not significantly increase the bacterial population.
It is therefore an object of the present invention to provide a bioremediation method and system for groundwater treatment that is more effective than prior bioremediation systems.
It is another object of the present invention to provide a bioremediation method and system for groundwater treatment that is less expensive than prior bioremediation systems.
It is still another object of the present invention to provide a bioremediation method and system for groundwater treatment that treats contamination naturally and effectively.
It is still another object of the present invention to provide a bioremediation system that is relatively easy and inexpensive to install and operate.
It is a related object of the present invention to provide a bioremediation system that can be installed with minimal site disturbance.
In accordance with the above and other objects of the present invention a bioremediation method and system is provided. The method includes providing a plurality of injection points extending from above ground to a subterranean body of groundwater. Substantially pure oxygen is delivered to the plurality of injection points and into the subterranean body of groundwater until the level of contaminants in the groundwater is reduced or eliminated.
The system includes a plurality of injection points extending below ground such that they intersect a body of groundwater. The plurality of injection points are in communication with a supply of concentrated oxygen. The concentrated oxygen is conveyed to each of the plurality of injection points and into the groundwater. The system includes at least one monitoring well for evaluating the level of contaminants in the groundwater.